Tweak redis connection pool settings to use timeouts and keep-alive.
Rename redis_con to redis_client and tweak related testing hooks.
Set redis connection info on the right class (the pool).
Add a RedisIsolation incl. proper per-test flushdb cleanup.
Use utc times in rate limitation logic.
Use new RedisIsolation in test_limiter tests
Avoid time.sleep call inside the test_limitation loop.